What is the Minimum Roof Pitch for Asphalt Shingles?

Whether you are looking to replace your old, failing roof with a new one or need to know the pitch for getting a permit for an addition to your house, many factors come into play when selecting the proper roof. One of those is the minimum pitch for asphalt shingles. This post helps you know what the minimum roof pitch for asphalt shingles and the best roofing materials you can install for flat or low slope roofs is

What is the minimum roof pitch for asphalt shingles?

The minimum roof pitch is the shortest dimension of a roof. It is the measurement from one side of a roof to another (either side of an exterior wall or a corner) perpendicular to that line. In reality, all kinds of shingles are expected to have a certain slope for proper functioning. In most cases, 2/12(two inches for every 12 inches horizontal) is the minimum requirement. Every homeowner must know the minimum roof pitch required for asphalt shingles since water from rainwater or melted snow can drain slowly when the pitch is low. That can boost the opportunity of a potential lateral water peril. Roofing manufacturers recommend the best roof pitch to be between 2:12 to 4:14 for the lowest pitch for asphalt shingles installation.

To calculate the pitch of your roof, you will want to measure from the highest point on your roof to the lowest one and divide that number by the distance from one side of the roof to another. Subtract 2 inches for a 2:12 pitch and 3 inches for a 3:12 pitch.

Low-slope roofing materials

Flat or low slope roofs where their slope is less than four inches high and 12 inches horizontally need unique systems to curb leaks. Even if the roof protects your home or huge industrial building, you will prefer to select the best system for your structure: Currently, most low-slope roofs are installed with the following primary materials:


Thermoplastic Polyolefin(TPO) refers to a single-ply membrane with several intriguing qualities. Since it is made of plastic its seams might be heat welded for enhanced durability. TPO tends to withstand harsh weather conditions and provides flexibility for thermal contraction/expansion and building settlement. For instance, if you live in an area with direct sunlight on your roof and high temperature, you can select the TPO in white due to its ability to keep the interior of the building cooler and more reflectivity than black or other dark colors. Further, due to its strong hide, it can resist puncture, and although it is not impervious, it can withstand moderate hail.


Propylene Diene Terpolymer(EPDM), a modified rubber material, can offer numerous qualities to your flat roof system. Since it is flexible it can withstand numerous decades of differential settling cold/hot cycles of the building without any challenges. Since EPDM is inert, it can withstand most chemicals. In reality, it is used to line retention ponds and leach pits. It comes in white, although most people use black color. When you compare all the single-play membranes, you will realize that this one is the best at handling hailstones. Further, since EPDM is made of rubber, it can withstand punctures in normal conditions, but gravel embedded in the boot can damage the membrane, meaning it might work effectively in areas with heavy traffic. Most importantly, at 0.03 inches, this roofing material is very thin, providing a faster and easier installation.

Modified Bitumen

Most people consider modified bitumen an evolutionary cousin of built-up roofing systems installed on most low-slope roofs for more than ten decades. This roofing material comprises asphalt combined with plastic or polymerized rubber and reinforced with fiberglass to develop a rugged but flexible waterproof membrane. You can primarily use the modified bitumen on low-slope or flat commercial roofs. However, depending on the material and type, you can install modified membranes as part of a multi-ply or two-layer system. This roofing system is an excellent choice for flat roofs for several reasons, including that it provides excellent protection from the elements. In states that experience high winds or heavy rainstorms during the year, then this type of roofing is an excellent option for you to consider. It is also highly durable, waterproof, and can last for 30 years or more. That makes it one of the appropriate choices for a homeowner looking for durability and long-term performance.

Further, most modified bitumen roofing systems are fire safe and do not need to be treated with chemicals. In reality, shingles can become cold for people who live in winter zones due to their shape and size. When that happens mold can start to form. In order to prevent this from happening, homeowners can replace their shingles with modified bitumen roof systems which have been proven to be resistant to mold growth.


PVC Roof Systems are an excellent choice for low-slope and flat roofs. That is because these systems can be installed with no visible seams, which allows rainwater to quickly run off the roof, protecting your home from water damage and other issues. 

The Polyvinyl Chloride (PVC) system comprises four primary components: a membrane, a secondary coating, an insulation board, and an exposed protection film. A membrane is a waterproof material to keep water out of the building envelope. The insulation board provides thermal resistance for the system and ventilation tracks for air passages inside the housing space. Exposing protection film provides an external protective layer against UV rays from sunlight which may cause discoloration of components in contact with it. The secondary coating is often a bitumen solution that provides an extra layer of protection against water penetration. PVC can be an ideal membrane for roof covering, especially among restaurants that vent your kitchen to the roofing area. PVC has similar qualities to TPO, which explains why roofers have found it the best alternative to gravel and tar systems. It can also be health welded or bent, but its primary merit over TPO is that it can withstand several chemicals.

Built-up roofing

Like an EPDM watertight roofing system, a BUR roof is constructed using a continuous layer of waterproofing material to form the primary water barrier. The BUR layer consists of an insulating material made of fiberglass or rock wool and a plastic lining that prevents moisture damage to the underlying structure. In addition to these materials, a BUR system includes a high-quality synthetic underlayment and high-density felt for additional protection against water seepage. In other words, it encompasses numerous layers of scrim or reinforced felt adhered with hot liquid asphalt and covered with pea gravel to ensure that it offers UV protection. That keeps your attic dry and comfortable all through the year.

A BUR system is a perfect solution for flat and low-slope roofs when you do not want to install a complex roof structure. This option uses the same basic construction principles as an EPDM rubber membrane, using separate water sealant layers but with a built-up insulation (BUR) layer as the final step in the process. If you have access to natural light and ventilation, you may choose not to install any insulation on your flat or low-slope roof. If this is not the case then will want to take advantage of a BUR system that provides twice as much insulation as an EPDM membrane alone. Since the insulation layer is separate from the membrane, it can be installed over any existing roof with minimal demolition.

There are two answers if you are looking for the minimum roof pitch for shingles. The minimum roof pitch will be different depending on which type of roofing material you choose. Asphalt roofing shingles have a minimum pitch of 2/12, while other kinds of shingles, such are tires, have a minimum pitch of 7/12. However, both pitches are commonly used with the traditional asphalt shingle roof. The key is looking at the package or your contract to determine what your property requires when you order it.